The Environmental Protection Agency of the United States in America has established certain standards for energy efficiency and exhaust gas cleanliness. The most recent version of these standards is called “Tier 4”.
A device that has been proposed to meet these standards is what is called a “diesel particulate filter”. Diesel particulate filters filter diesel exhaust gas and remove microscopic particles of debris from that gas. Diesel particulate filters need to be periodically regenerated, preferably by temporarily elevating the temperature of the exhaust gas to temperatures approaching 600° C. At these temperatures, cellulose dust and other combustible debris will instantly incinerate.
The incineration of a small amount of debris typically found in engine compartments of over-the-road vehicles does not pose a problem. In other environments, such as off-road and agricultural operating environments, the risk may be greater.
Agricultural harvesting typically occurs in fields of dry crop. The basic function of an agricultural harvester is to cut down dry crop plants, shred them, separate seeds from the undesirable portions of the plant, and blow the unwanted plant material out the back of the harvester, spreading it over the ground where it can nourish the soil.
Harvesting typically occurs in blustery, gusting, and windy conditions. Under these conditions, a significant portion of the unwanted crop material is levitated and pulled into the engine compartment. This levitated unwanted crop material varies in size from dust particles to entire leaves of the plant, and over time it will coat the entire engine compartment. This coating occurs in spite of the traditional air flows through the engine that are generated by cooling fans, for example.
The diffuse air flows generated by cooling fans lack the velocity to keep the unwanted crop material from settling on cool components in the engine compartment and building up in a thick layer.
Hot components, such as mufflers and exhaust pipes do not pose a problem, since the unwanted crop material never builds up on them. To the extent the muffler is hot enough to incinerate unwanted crop material, that material (typically dust or fine leaf particles) is carbonized as soon as it touches the muffler and never builds up in sufficient volume to catch on fire.
The particular problem posed by diesel particulate filters is due to their intermittent operation: long periods of relatively low temperature (during normal operation) interspersed with short periods of extremely high temperatures (during the regeneration cycle).
During the long periods of normal operation in which the diesel particulate filter is relatively cold, unwanted crop material can build up on the outside surface of the filter. When the regeneration cycle begins and the diesel particulate filter becomes extremely hot, this now-thick layer of unwanted crop material may combust.
One solution to this problem is to surround diesel particulate filters with a thick insulating layer. If it is thick enough, the outside layer of the insulation will never reach an incinerating temperature. Added layers of insulation, however, increase the size and the cost of diesel particulate filters as well as make the diesel particulate filters difficult to fit into engine compartments with closely packed components.
Another solution is to intermittently remove accumulated unwanted plant material from the surface of the diesel particulate filter prior to its regeneration cycle, for example by providing a mechanical member to wipe the surface of the diesel particulate filter, or a separate blower that can be periodically energized to blow the accumulated unwanted crop material off the surface of the diesel particulate filter prior to its regeneration cycle. Unfortunately this also adds significant cost of the vehicle. They require the addition of a high power fan capable of blowing a layer of accumulated unwanted crop material off the diesel particulate filter and intelligent electronic control circuitry to turn the fan on and off at the appropriate times.
What is needed, therefore, is an engine compartment arrangement for an agricultural Harvester that will prevent the accumulation of combustible plant material on a diesel particular filter.
It is an object of this invention to provide such an engine compartment arrangement.